Variable resistor and switch combination



M. DAILY VARIABLE RESISTOR AND SWITCH COMBINATION 4 Sheets-Sheet 1 Filed Feb. 5, 1,954

I. AriZ-zur M Daily Aug. 28. 1956 A. M. DAILY VARIABLE RESISTOR AND SWITCH COMBINATION 4 Sheeds-Sheet 2 Filed Feb. 5, 1954 Arfihur .UazZy I. MM

Aug. 28, 1956 A. M. D AlLY VARIABLE RESISTOR AND SWITCH COMBINATION 4 Sheets-Sheet 3 Filed Feb. 3, 1954 J WMKM Ari hm" M. .UazZy lbx. MW?

Aug. 28, 1956 A. M. DAILY 2,761,044

VARIABLE RESISTOR AND SWITCH COMBINATION Filed Feb. 3, 1954 4 Sheets-Sheet 4 b Jam #524 ATZZmrMEazZy Unitd States Patent VARIABLE RESISTOR AN D SWITCH COMBINATION Arthur M. Daily, Edwardsburg, Mich., assignor to Chicago Telephone Supply Corporation, Elkhart, Ind., a corporation of Indiana Application February 3, 1954, 'Serial No. 407,901

8 Claims. (Cl. 201--55) operating shaft which extends forwardly through a hole in the base.

The spring contact fingers in reacting against the resistance element and collector ring impose an inward end thrust upon the rotatable assembly which, of course, must be limited to assure proper contact pressure between the resistance element and the spring fingers which ride thereon. Herctofore, it has been customary to resist such end thrust and define the axial position of the retartable assembly by a C washer fitted into an annular groove ,in the operating shaft and bearing against the front end of a bearing'bushing mounted on the insulated bases Obviously, such a construction requires additional and relatively expensive parts, but more important it cannot be used where the operating shaft is rolled up from sheet material to save cost since the required groove cannot be formed in a hollow shaft without objectionably weakening the shaft. To meet this condition the end Wall of the cover which forms part of the housing enclosing the instrumentalities of the resistor has been employed to carry the inward end thrust imposed upon the rotatable assembly. However, in the past this expedient could not be used in a tandem arranged resistor-switch combination since the relatively large hole in the end wall of the resistor housing which is necessary to accommodate the switch operating connection between the resistor and the switch so weakened this end wall that it could not be depended upon to accurately define the axial position of the rotatable assembly. This weakness was es pecially significant in situations where the operating shaft of the combination control was apt to be subjected to accidental and relatively severe inward end thrust.

In recognition of the desire to obviate the conventional G washer, and with a view toward overcoming the weak ness in the end wall of the resist-or cover caused by the necessary hole therein, it is an object of this invention to so construct the cover that it has the strength needed to carry any end thrust which might be imposed upon the rotatable assembly of the resistor without deforma tion and thereby assure the maintenance ,of the desired spring contact pressure, despite the presence of the hole in the end wall.

Another object of this invention is to provide a vari able resistor of the character described wherein adequate side thrust bearing support is provided for its rotatable contactor assembly by journalling the opera-ting shaft in a bearing hole in the insulated base and supporting the inner end of the assembly by means of a pilot pin or stem which connects the rotatable assembly with the end wall of the housing and preferably projects from the rotatable assembly and is journalled in a bearing hole in the end wall, and more specifically in the apex of an inwardly directed, substantially conical embossment in the end wall.

Another object of this invention is to provide an end thrust bearing for the rotatable contactor assembly of a variable resistor which in addition to accurately locating the axial position of the contactor is exceptionally smooth in operation due to a significant reduction in frictional resistance to rotation.

Another object of this invention is to provide a variable resistor of the character described in which the ro tatable contactor assembly is especially adapted to be driven by a hollow rolled shaft either permanently or detachably connected to the assembly.

Still another object of this invention resides in the provision of a novel rotatable contactor assembly having an insulated contactor carrier or drive arm and a stamped metal stop plate disposed in overlying relationship and secured together by a rivet which also provides a pilot pin or stem to be journalled in a bearing in the end wall of the resistor housing.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of the physical embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view partially in side elevation and partially in longitudinal section through a combined variable resistor and switch embodying one form of this invention;

Figure 2 is a perspective view of the control shown in Figure l but with the instrumentalities of the resistor removed to better illustrate the inside aspect of the end wall .of the resistor housing;

Figure 3 is a perspective view of the rotatable contactor assembly of the control shown in Figure l illustrating the same primarily from its inner end;

Figure 4 is a front view (on a smaller scale) of the control shown in Figure 1;

Figure 5 is .a view similar to Figure l but illustrating a modified embodiment of the invention;

Figure 6 is a perspective view similar to Figure 2 illustrating particularly the inside of the resistor housing cover of that form of the invention shown in Figure 5;

Figure 7 is aperspective view of the rotatable contactor assembly of that form of the invention shown in Figure 5;

Figure ,8 is a view similar to Figure 1 illustrating still another embodiment of the invention;

Figure 9 is a perspective view similar to Figure 2 but showing the inside of the resistor cover of that form of the invention shown in Figure 8;

Figure 10 is a perspective view of the rotatable contactor assembly which forms part of the embodiment of the invention shown in Figure 8;

Figure 11 is a view partially in side elevation and partially in longitudinal section similar to Figure l illustrating still another embodiment of this invention; and

Figure 12 is a perspective view of the rotatable con tactor assembly of that .form of the ;.i.nve.ntio n shown in 3 Figure 11, and its operating shaft which in this instance is detachable.

Referring now particularly to the accompanying drawings in which like numerals designate like parts throughout the several views, the numeral 5 indicates generally a variable resistor of the type commonly employed in radio and television receivers and the numeral 6 indicates generally a switch which is mounted on the back of the resistor so that the two units are arranged in tandem to be actuated by a common control shaft 7.

The specific switch mechanism forms no part of this invention and hence has not been illustrated. Moreover, the switch may be of any suitable form as long as it is capable of being actuated during part of the rotation of the rotatable contactor assembly indicated generally by the numeral 8 which, as is customary, con stitutes an essential part of the resistor instrumentalities. To this end the switch 6 is mounted on the back of the resistor housing and has an operating unit 9 often referred to in the art as a switch operating cam arranged to project into the interior of the resistor housing through a hole 10 in the housing end wall 11.

The switch operating unit or cam 9 is adapted to be transiently engaged by a lug 12 which extends rearwardly or inwardly from a stamped metal stop plate 13 and which in turn is part of the rotatable contactor assembly.

The instrumentalities of the variable resistor in addition to the rotatable contactor assembly 8 include what might be considered a stator assembly consisting of a base 14 of insulating material the inner face of which mounts a flat split ring-shaped or arcuate resistance element 15 and a metal collector ring 16. Where the resistance element comprises the customary separate part, as shown, it is held in place on its base by its terminals 17. The collector ring 16 is likewise held in position by its terminal 18.

The base 14 coacts with a stamped cup-shaped cover or shell 19 to provide the housing for the instrumentalities of the control and accordingly has the marginal edge portion of its cylindrical side wall securely connected to the base 14. The securement of the cover to the base 14 also holds in position a metal ground plate 20 which overlies the front face of the base and has a hole to accommodate the shaft 7. The ground plate preferably has twist-type attaching ears 21 formed thereon or some other suitable means of fastening the control to the back of a mounting panel with its shaft 7 protruding therethrough.

in that form of the invention illustrated in Figures 1 to 4, inclusive, the only side thrust bearing for the rotatable contactor assembly is provided by having the shaft 7 journalled in a bearing hole 22 in the insulated base 14. it is, of course, understood that the bearing hole 22 is coaxial with the resistance element 15 and the collector ring 16 so that upon rotation of the shaft the spring contact fingers 23 of the rotatable contactor assembly will traverse the resistance element and collector ring in the customary and proper manner.

The inward end thrust imposed upon the rotatable contactor assembly by the spring contact fingers is resisted and limited in a way which obviates the need for the conventional C washer heretofore usually employed to carry the end thrust, and which instead utilizes the rear or end wall 11 of the stamped cover or shell 19. If the only end thrust that would have to be considered was that resulting from the spring contact fingers, the end wall 11 might be strong enough if left fiat as has been the practice heretofore despite the fact that the hole 10 therein greatly weakens the same, but as those skilled in the art well know, a control of this character must be designed to withstand accidental and sometimes even intentional inward end thrust imposed upon the shaft 7 by external force. To meet this eventuality, the present invention reinforces the end wall 11 by forming the same with an inwardly directed, substantially conical central embossment or indentation 24, the apex of which is positioned to have the center of the stop plate 13 (which forms part of the rotatable contactor assembly) bear thereon. The apex of the embossment or indentation is smoothly rounded and thus has practically a single point contact with the stop plate. This provides a thrust bearing of minimum frictional drag which, of course, is conducive to smooth operation.

It is to be noted that the hole 10 which accommodates the switch operating unit or cam 9 is partly in the embossment or indentation and that the base diameter of the embossment or indentation is small enough not to interfere with the tangs or ears 25 which extend forwardly from the side wall of the switch cover through slots in the end wall 11 and are bent over, as shown in Figure 2, to hold the two units together.

in that form of the invention shown in Figures l to 4, inclusive, the shaft 7 is hollow being preferably rolled up from a stamped sheet metal blank and is permanently se cured to the rotatable contactor assembly by three circumferentially spaced tongues 26 which extend through aligned slots in the insulated drive arm 13 and the stop plate 13 and are riveted or staked over the inner face of the stop plate as best shown in Figure 3. Thus the securement of the shaft to the rotatable contactor assembly also serves to hold these elements of the rotatable assembly together.

As indicated, that form of the invention shown in Fig ures l to 4, inclusive, provides only a single side thrust bearing for the rotatable contactor assembly. All of the other embodiments of the invention illustrated provide a second side thrust bearing in the form of a pilot stem or pin 30 extending axially from the inner end of the rotatable contactor assembly and journalled in a bearing hole in the apex of the embossment or indentation 24.

In the structure shown in Figures 5, 6 and 7, this pilot stem or pin 30 constitutes the innermost end of the operating shaft 7' which in this case is solid. The attachment of the shaft 7 to the stop plate 13 and the insulated drive arm 13' is afforded by a non-circular section 31 on the inner end of the shaft fitting in these overlying elements with its outer end portion riveted or swaged down as at 32 to hold the parts assembled. The stem or pin 30 projects from the center of the riveted portion but leaves a flat surface 33 at the base of the pin to ride upon the apex of the embossment or indentation defining the edge of the bearing hole. This results in a smooth end thrust hearing as well as a second side thrust hearing which together with the bearing provided by the hole 22 in the base supports the rotatable contactor assembly against any possible displacement from correct position.

In the modification of the invention illustrated in Figures 8, 9 and 10, the location of the various parts is substantially as that already described, except for the further improvement of greater axial length in the side thrust bearing which the end wall 11 of the resistor housing cover provides. Thus, as shown, the margnial edge portion of the bearing hole in the apex of the embossment or indentation is extruded to provide a cylindrical bearing 35. The stop plate 13 is similarly extruded to provide the pilot stem or pin 30.

In this case the operating shaft is hollow and is secured to the stop plate and drive arm of the rotatable contactor assembly in a manner similar to that employed in the embodiment of the invention shown in Figures l to 4, inclusive, but since the end thrust in this case is transmitted to the embossment or indentation by the riveted inner ends of the tongues 26, an antifriction washer 36 encircles the extruded bearing 35 to lie between the riveted ends of the tongues 26 and the adjacent surface of the embossment or indentation.

The modification shown in Figures 11 and 12 is characterized by two features, one of which is the detachability of its operating shaft 7" and the other of which resides in the specific construction of the pilot stem or pin 37. As clearly shown in Figure 11, the stem or pin 37 is part of a rivet which serves to hold the stop plate 13 and the insulated drive arm 13' together and has an enlarged medial portion 38 providing a shoulder 39 to bear on the apex of the embossment or indentation around the marginal edge of the bearing hole therein.

To provide for the detachable driving connection between the shaft and the rotatable contactor assembly, the overlying stop plate 13 and drive arm 113 have diametrically opposite slots or holes 40 therethrough into which project spring fingers 41 extended from the inner end of the operating shaft. These fingers are shaped to provide detent shoulders 42 which engage over the edges of the holes .9 in the metal stop plate and thereby draw the end 43 of the shaft firmly against the front face of the insulated drive arm.

As is customary, in all of the embodiments of the invention illustrated the stop arm 13 has a lug as which coacts with an abutment 45 formed in the housing of the variable resistor to limit the rotation of the rotatable contactor assembly.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art that this invention solves a problem recognized by the industry for quite some time and that its solution of this problem has the significant attribute of simplicity and low cost.

What I claim as my invention is:

1. A combination variable resistor and electric switch, the resistor being enclosed within a housing including a stamped metal cup-shaped cover having an end wall which separates the resistor instrumentalities from the switch mechanism, the switch being mounted on the exterior of said end Wall of the cover, the variable resistor including a rotatable assembly with an operating shaft accessible at the front of the resistor housing, the switch mechanism having an operating unit entering the housing of the variable resistor through a hole in the end wall of its cover for actuation by the rotatable assembly of the variable resistor, said resistor-switch combination being characterized by: the fact that the end wall of the resistor housing cover has a central inwardly directed embossment against which the rotatable assembly bears so that said embossment carries inward end thrust imposed upon the rotatable assembly; and further by the fact that the hole in the end Wall through which the switch operating unit enters the resistor housing is partially in said embossment.

2. The resistor-switch combination of claim 1 further characterized by: a pilot pin connecting the rotatable assembly with the center of the embossment so that said embossment provides both an end thrust bearing and a side thrust bearing for the rotatable assembly.

3. The resistor-switch combination of claim 2 wherein the pilot pin extends axially from the rotatable contactor assembly and is journalled in a hole in the center of the embossrnent, further characterized by: the provision of means on the rotatable assembly providing an end wall at the base of the pilot pin, said end wall bearing against the central portion of the embossment encircling the hole in which the pilot pin is journalled.

4. The resistor-switch combination of claim 3 further characterized by: the fact that the edge portion of the hole in the embossment in which the pilot pin is received extends inwardly to provide a cylindrical bearing for the pilot pin.

5. A tandem arranged variable resistor and electric switch combination of the character described and wherein said two units are separated by a stamped metal wall having a hole therein through which the switch operating unit passes to enable actuation of the switch by the rotatable assembly of the variable resistor, characterized by: the fact that said stamped metal wall is shaped to provide a central embossment facing toward the variable resistor and having its central portion bearing against the adjacent end of the rotatable assembly of the resistor; and further by the fact that the hole in the end wall through which the switch operating mechanism passes is partially in said embossment, the embossment giving the end wall sufficient strength to carry inward end thrust imposed upon the rotatable assembly of the resistor despite the presence of said hole in the end wall.

6. A variable resistor, comprising: a flat base of insulating material having a resistance element mounted thereon and having a hole therethrough; a rotatable assernbiy for the resistor including a spring contact finger riding on the resistance element and an operating shaft journalled in the hole in the base, the reaction of the spring contact finger against the resistance element imparting an inward end thrust to the rotatable assembly; a cup-shaped cover for the instrumentalities of the resistor including an end Wall and a side wall, the latter being connected to the base so that the base coacts with the cover to provide a housing for the instrumentalities of the resistor; a central inward embossment in the end wall having a hole at its center coaxial with the bearing hole in the base; the area of the end wall surrounding the embossment being substantially flat; a pilot pin projecting axially from the rotatable assembly and journalled in the hole in the embossrnent so that the rotatable assembly is supported against side thrust jointly by the base and the end wall of the cover; means on the rotatable assembly providing an end bearing surface which bears against the portion of the embossment bounding the hole therein so that inward end thrust imposed upon the rotatable assembly is carried by the end Wall of the cover and which by virtue of its embossment is reinforced against such inward end thrust; and the end wall of the cover having a hole therein through which an actuating connection may be made between the rotatable assembly and mechanism to be actuated thereby, mounted on the exterior of said end wall, said hole substantially straddling the junction of the embossment and the substantially flat portion of the end wall surrounding it so that the hole is partially in the embossment and partially in the substantially flat surrounding portion of the end wall.

7. The variable resistor of claim 6 further characterized by: the fact that the rotatable assembly includes a metal stop plate and an insulated drive arm in overlying relation with the drive arm confined between a shoulder on the operating shaft and the stop plate; and further by the fact that said overlying stop plate and drive arm are secured to the shaft by a non-circular portion of the shaft passing therethrough, the outer end of which is staked over the end plate and has the pilot pin integral therewith and projecting axially therefrom.

8. The variable resistor of claim 6 further characterized by: the fact that the rotatable assembly includes an insulated drive arm and a metal stop plate in overlying relation and by the fact that the pilot pin has a portion thereof which serves as a rivet to secure said drive arm and stop plate together and also has an end thrust surface bearing against the embossment to carry the end thrust from the rotatable assembly into the end wall.

Meuer Sept. 12, 1939 Budd Feb. 10, 1953 

